The present invention generally relates to the fabrication of water heaters, and more particularly relates to the installation of an externally jacketed foam insulation structure around the storage tank portion of a water heater.
Modern water heaters typically include a storage tank portion adapted to hold a quantity of heated water for on-demand supply to plumbing fixtures such as sinks,, tubs, and showers. Projecting outwardly from the storage tank are pipe coupling fittings threadingly connectable to a cold water inlet pipe, a hot water supply pipe, and a temperature/pressure relief pipe. The storage tank is externally insulated by injecting liquid insulating foam into an enclosed insulation space formed between the exterior surface of the storage tank and an external jacket structure disposed outwardly around the storage tank. Piping connections to the storage tank couplings are made through openings formed in the jacket which are spaced outwardly from the couplings in facing relationships with their outer ends.
During the insulating foam injection process it is necessary to prevent the foam from escaping outwardly through the jacket structure pipe connection openings and/or entering the open outer ends of the storage tank pipe coupling fittings. Using conventional methods, this is typically accomplished in two ways. The first method is to provide a fiberglass block having holes formed therethrough to receive the storage tank couplings, position the block against the storage tank exterior with the couplings received in the block holes, and then install the jacket structure. During subsequent injection of the insulating foam the fiberglass block serves as a barrier within the enclosed insulating space to prevent the foam from being forced out through the jacket structure pipe connection openings or entering the storage couplings.
While this is a relatively simple and straightforward approach to forming foam stop barriers, it has two primary disadvantages. First, the fiberglass block must be very carefully sized to sealingly extend between the outer surface of the storage tank and the inner surface of the jacket structure. If even a slight gap exists around the installed block it can easily permit the injected foam to escape from the jacket structure or enter the pipe couplings.
Second, the fiberglass block, which tends to be relatively large, typically has a thermal insulation value only about half that of the insulating foam. Accordingly, relative to the foam insulation, the fiberglass block forms a relatively low resistance heat outflow path in the assembled water heater. As energy conservation goals and standards continue to increase, this situation becomes less and less acceptable.
The other method conventionally used to form a foam stop barrier around the tank couplings and their associated jacket structure pipe connection openings has been to construct a relatively flat, foam-filled bag having openings therein through which the tank couplings may be extended, taping the bag blanket-like to the tank exterior, and then installing the jacket structure over the bag. Since the bags are filled with foam insulation, they do not present the heat leak problem that the fiberglass blocks do. However, like the fiberglass blocks, the foam filled bags present the potential problem of injected foam leakage past the bags if they are not carefully sized and properly fitted into place within the enclosed insulation space before the foam injection process is initiated. Additionally, the bags are rather tedious and time consuming to fabricate and install, thus undesirably increasing the overall construction cost of the water heater.
It can be readily be seen from the foregoing that a need exists for improved foam stop apparatus and methods in the fabrication of externally foam-insulated water heaters. It is accordingly an object of the present invention to provide such improved foam stop apparatus and methods.